One of the secrets of a good book is a curious author. Consider this from Matt Ridley: “I walk a lot in London, and a few months ago I set myself a goal: somewhere in the vast city, while walking down a street, to catch the smell of sewage. I have yet to achieve this goal. Close to ten millions defecations occur in London every day, presumably, for most people it is daily occurrence. I hazard that I am rarely...